1. Field of the Invention
The present invention relates generally to a real-time face detection apparatus, and, more particularly, to a face detection apparatus for detecting the positions and sizes of one or more faces in an image, captured by a camera, by analyzing the captured image using a window in real time.
2. Description of the Related Art
In the case where a general image processing scheme is used, captured faces have a variety of sizes and shapes. Face detection under various limitations to, for example, the position of a face and illumination, can be implemented using a relatively simple method. In images captured in a general environment, faces are variously deformed according to the environment. The environment makes it difficult to detect faces in the captured images.
Furthermore, a person may exist at one of various positions with respect to a camera placed at a specific position. Accordingly, this results in a change in the size of a face in an input image. In order to detect the face, it should be determined whether a region having a variable size is a face region or not. This determination is not easy in general image processing methods.
In order to solve this problem, P. Viola and M. Jones proposed a method of constructing specific classifiers based on facial features, dividing the specific classifiers into weak classifiers at a plurality of levels, and performing face detection using strong classifiers, which are combinations of the weak classifiers. In particular, a small number of classifiers are assigned to the early stage of the strong classifiers, and a large number of classifiers are assigned to the later stage of the strong classifiers, so that both the detection speed and performance are improved compared to those of the prior art.
However, this method is also performed sequentially based on software, so that in order to detect faces having various sizes, images must be sequentially scaled and face detection must be performed on the scaled images based on respective strong classifiers, with the result it is generally difficult to process images necessary for image processing in real time.